1. Field of the Invention
The present invention relates to a steering wheel and particularly to a steering wheel provided with an air bag apparatus.
The present application is based on Japanese Patent Application No. 2000-308860, which is incorporated herein by reference.
2. Description of Related Art
Conventionally, a steering wheel of this type is formed by a core member, as a base material, covered with resin or the like. As the core member, for example, one shown in FIG. 5 is used.
This core member 100 is constituted by a boss plate 101 connected to a steering shaft not shown, an annular rim 102 with the boss plate 101 as a center, and a plurality of spokes 103 connecting the boss plate 101 and the rim 102.
In the case where the spokes 103 are provided by three, for example, these spokes may be provided in the following mode.
That is, of these three spokes 103, a first spoke 103a and a second spoke 103b are disposed to be arranged substantially linearly through the boss plate 101 when those spokes are viewed from the front of the steering wheel. On the other hand, the third spoke 103c is provided in such a position that, with the boss plate 101 as a center of rotation, the first and second spokes 103a and 103b are respectively rotated by about 90 degrees counterclockwise and clockwise respectively. The end portion of the third spoke 103c at the boss plate 101 side is made to branch off into two tines the ends of which are connected to the first and second spokes 103a and 103b respectively.
Further, an air bag module 104 provided with a not-shown inflator, an air bag, or the like, is disposed above the boss plate 101 of the core member 100 configured thus. Here, with the steering shaft in a neutral state, where rotating operation is not carried out, a middle line m, which intersects a center axis line of the steering shaft so as to divide the steering wheel into upper and lower portions, is defined as follows. The air bag module 104 in the steering wheel is fixed by means of screws and through holes 105. The through holes 105 are formed in the first and second spokes 103a and 103b and are substantially on the above-mentioned mentioned middle line m. When an impact exceeding a predetermined range acts on the vehicle, the air bag accommodated in the air bag module 104 is deployed to receive a passenger. In the conventional steering wheel, however, as shown in FIGS. 6A and 6B, a large load in the vehicle forward direction as indicated by an arrow in the drawing may act on the lower end portion of the rim 102 of the core member 100 due to a change in posture of the passenger. If such a large load acts on the rim 102 of the steering wheel, the rim 102 may be deformed.
However, the air bag module 104 is attached to the first and second spokes 103a and 103b and on the middle line m of the steering wheel as described above. Here, for example, a case where a large load acts on the lower side of the steering wheel, while in the neutral state, in which the steering wheel is not rotated, is considered. In such a case, because the first and second spokes 103a and 103b of the core member 100 are very rigid, the steering wheel is deformed and bent with respect to the axial line of the first and second spokes 103a and 103b. Hence, it might occur that the air bag module 104 is not displaced in accordance with the deformation of the rim 102, and the lower end of air bag module 104 may separate from the steering wheel. This situation changes the direction of the air bag deployment with respect to the advancing direction of the passenger, and there is a fear that the impact absorption effect will be lowered.
The present invention has been achieved by paying the attention to such a problem in the background art. It is an object of the present invention to provide a steering wheel in which the development direction of the air bag is changed in accordance with deformation of the steering wheel.
In order to achieve the above object, the invention has a gist in that a steering wheel is constituted by: a boss portion connectable to a steering shaft; a rim portion provided to surround the boss portion; a spoke portion connecting the boss portion and the rim portion to each other; and an air bag module; wherein the spoke portion include a first, a second and a third spoke cores, the first and second spoke cores being arranged substantially linearly through the boss portion so as to continue uninterruptedly with each other when the steering wheel is viewed from a front side thereof, the third spoke core being arranged so as to connect the first and second spoke cores to the rim portion in a direction substantially perpendicular to an extending direction of the first and second spoke cores; and wherein the air bag module is provided with a fixing position at a position apart from a center line extending in the longitudinal direction of the first and second spoke cores.
In the invention, even if the steering wheel is deformed due to large load acting on the steering wheel, the air bag module is easily displaced in accordance with the deformation of the steering wheel. Further, in accordance with the displacement of the air bag module, the direction of developing the air bag received in the air bag module is changed.
In the invention, lower ends of the first and second spoke cores may be located substantially above a middle line which passes on a center axis of the steering shaft so as to divide the steering wheel into the upper and lower portions, in the neutral state of the steering wheel.
By the above structure, the difference in rigidity between respective portions of the rim portion becomes small, so that the difference in displacement between rotation positions of the steering wheel can be reduced.
In the invention, a branch portion bifurcated to provide two tines may be formed at an end of the third spoke core in a manner so that forward ends of said two tines are connected respectively to said first and second spoke cores and so that, when said steering wheel is viewed from the front side thereof, said two tines and said first and second spoke cores intersect each other obliquely in plane view.
By the above structure, the difference in rigidity between respective portions of the rim portion can be reduced, and the quantity of material for the third spoke core can be reduced so that the weight of the steering wheel can be reduced.
In the invention, the air bag module may be fixed to the branch portion in the third spoke core.
The air bag module can be displaced surely in accordance with the deformation of the steering wheel.
In the invention, in an air bag module fixing portion in the spoke cores, a reception seat on which the air bag module abuts partly may be provided.
In the above structure, when the air bag module is attached to the spokes, the air bag module abuts on the reception seat so that the air bag module can be attached stably.